Synchronized control apparatus for hydraulic heavy weight lift

ABSTRACT

A hydraulic heavy duty lift of the multicylinder type may be operated in the most stable and efficient manner in accordance with the synchronized control apparatus of this invention in which the control apparatus comprises interconnected hydraulic motors, independent flow rate compensating circuits for the hydraulic motors, release circuits to release the excess liquid in preceding cylinders at the highest terminal position, a common adjusting circuit for even loading at the starting position, liquid feeding circuits to avoid the evacuation caused by the preceding cylinder at the lowest terminal position.

United States Patent [72] Inventors App]. No. Filed Patented Shoichi Tani 12-1 Ozawamicho;

Yoshikazu Horikawa, 8-1, l-chome, Ozawamicho, both of Tobata-ku, Kitakyushu-shi, Fukuoka-pref.; Ichiro Goshima, 2-ch0me, Tenjin-sho, Yawata-ku, Kitakyushu-shi, Fukuoka-pref.; Kiyomitsu Arakl, 2-17, Minamikamato; Yoshitake Nakamura, 3-32-16, Omoriminami, both of Ota-ku, Tokyo, all of Japan Dec. 5, 1969 Dec. 7, 1971 Continuation-impart of application Ser. No. 808,809, Mar. 20, 1969, now abandoned. This application Dec. 5, 1969, Ser. No. 882,492

SYNCHRONIZED CONTROL APPARATUS FOR HYDRAULIC HEAVY WEIGHT LIFT 2 Claims, 1 Drawing Fig.

US. Cl

[51] Int. Cl FISb 11/22 [50] Field of Search 91/411 R, 411 B,4l2;60/97E [56] References Cited UNITED STATES PATENTS 1,831,238 11/1931 Ferris 60/97E 3,448,577 6/1969 Crawford 60/97 E 3,509,721 5/1970 Crawford 60/97 E Primary Examiner-Edgar W. Geoghegan At!0rney Linton & Linton ABSTRACT: A hydraulic heavy duty lift of the multicylinder type may be operated in the most stable and efficient manner in accordance with the synchronized control apparatus of this invention in which the control apparatus comprises interconnected hydraulic motors, independent flow rate compensating circuits for the hydraulic motors, release circuits to release the excess liquid in preceding cylinders at the highest terminal position, a common adjusting circuit for even loading at the starting position, liquid feeding circuits to avoid the evacuation caused by the preceding cylinder at the lowest terminal position.

PATENTEU 0E6 71971 INVENTORS 05H lk/kZu HORIKAWA,

U MA A K] AND BY ATTORNEYS SYNCHRONIZED CONTROL APPARATUS FOR HYDRAULIC HEAVY WEIGHT LIFT The present application is a continuation-in-part of our pending application, Ser. No. 808,809, filed Mar. 20, 1969, now abandoned.

This invention is concerned with a control system for lifting and lowering heavy weight apparatus, such as a converter, safely and surely by a number of hydraulic cylinders. Such use is not limited to converters, but may be used for other heavy equipment also.

BACKGROUND OF THE INVENTION It is usual to repair or change inner refractories of converters periodically in the operation of a metallurgical refining converter and the like.

Heretofore, it has been conventional procedure to make repairs or changes thereof on the spot through the temporary interruption of the operation of the converter. Therefore, either one of the two furnaces of one of the three sets of equipment is compelled to be closed down while undergoing repairs. In order to avoid such inefficient interruptions, a method was lately developed to enable normal operation to continue by replacing the furnace to be repaired with another operational furnace.

However, many problems are yet to be solved in displacing furnaces rapidly and safely, owing to the heavy weight of the steel converters that have been developed on an industrial scale, which often weigh more than hundreds of tons.

It is rather difficult to equip a lift with a guide owing to the structure of the device. The hydraulic cylinders themselves, however, must have guides which simultaneously act as the lift apparatus. Therefore, in order to avoid upsetting the upper loaded furnace by an unbalance in synchronization of the four cylinders, it is necessary to closely control them, and the cylinders must be provided with means to restore them from their unbalanced condition in the shortest possible time.

Causes for the unbalance of synchronization of the said hydraulic lifting apparatus are as follows:

1. An unbalance of rotation among the hydraulic motors in the hydraulic circuit.

2. Structural difference between each motor.

3. An unbalance of pressure distribution caused by unequal extension of the cylinders.

4. Unbalance of the cylinders at the termination of the lifting or lowering position.

5. Unbalance phenomena in the cylinders at the commencement of their operation.

DESCRIPTION OF THE INVENTION The present invention provides a synchronized control ap paratus which can solve the drawback of known lifts as described above.

Therefore, an object of this invention is to provide an improved and satisfactory synchronized control apparatus for hydraulic heavy duty lifts.

It is also an object of this invention to provide a synchronized control apparatus to lift and lower heavy weight materials safely by removing the causes for the unbalance in the process of the synchronization of the cylinders, which occur in hydraulic lifting apparatus.

The structure by means of which the above noted and other objects and advantages of the present invention are attained will be described in the following specification, taken in conjunction with the accompanying drawing, showing a preferred illustrative embodiment of the present invention.

The drawing shows a schematic diagram of the synchronized control apparatus for the hydraulic heavy duty lift of this invention.

The lift is explained in reference to the drawing embodying a four cylindered lifting apparatus for a load.

l. As a synchronizing apparatus designed to remove the danger of only one cylinder ascending independently, four hydraulic motors 2, 3, 4 and 5 are placed in the main circuit extending to each of the cylinders 6, 7, 8 and 9, respectively, and shaft couplings a, b and c are connected to the said motors mutually for the purpose of evenly delivering the output liquid of the main hydraulic pump 1. The term hydraulic motor is intended to cover a reversible motor which pumps when driven.

Owing to the fact that the drawing is shown as a more schematic diagram, the four cylinders are drawn in plane view and only three shaft couplings are illustrated. In an actual arrangement, it is desirable to join the motors 2 and 5 together. Moreover, the advantage of this apparatus exists, besides the above-mentioned synchronizing fidelity, in the capability of effectively distributing liquid pressure from a cylinder bearing a heavier load to a cylinder for a lighter load, through the hydraulic motors and the shaft couplings by which a lesser driving torque than other apparatus, such as those controlled only by flow rate control valve attached with the pressure compensator, is obtained. 2. For the purpose of adjusting the differences between individual motors used in said synchronizing apparatus, a flow rate compensating circuit is provided in each of the hydraulic main circuits to superpose and equalize the quantity of oil in each circuit for maintaining the same height for all pistons of the cylinders, that is to say, to feed preliminarily adjusted and fixed amounts of oil for the equalization of any differences among the hydraulic motors.

In other words, flow rate control variable restrictors with pressure compensators l0, 1 I, 12 and 13 such as, for example, Vickers Detroit Pressure Compensated Flow Controls; models FG-02, FG-03, FG-06, or FG10 of Vickers Sperry Rand, Limited, the function and structure of which are shown in handbooks such as "Hydraulic Handbook published by Trade'and TechnicalPress Ltd. Morden, Surrey, England at FIGS. 242 and 243, Pages 146-147 are interconnected between the motors 2, 3, 4 and 5 and the cylinders 6, 7, 8 and 9, respectively, and these circuits are combined together into one compensating circuit which is connected to auxiliary pump 14 through the solenoid valve 15, whose function is to change the flow direction in reverse from lifting to lowering as explained later, and the relief valve 16. Assuming that the differences in the feed of oil by motors 2, 3, 4 and 5 is 5 percent, that is to say, assuming that hydraulic motors 2, 3, 4 and 5 are designed to feed oil at the rate of 100 liter/min; respectively to lift the pistons of cylinders 6, 7, 8 and 9, but one of the motors feeds only liter/min. (5 percent less than nominal capacity) owing to the mechanical difference of the motor, the necessary amount of oil to equalize the height of the piston, moved thereby with the other pistons namely 5 liter/min; is added through the flow rate control variable restrictor l0, l1, 12 or 13 connected thereto, which is preliminarily adjusted before operation of the lifting apparatus to compensate for the 5 percent difference in feed of the motor by feeding oil at the rate of 5 liter/min; and the difference in compensating oil flow of the flow rate control variable restrictors with pressure compensators 10, ll, 12 and 13 will be 5 percent. That is to say, the additional feeding of oil through said flow rate control variable restrictor will be 4.75 liter/min; with the resulting difference being as low as 0.25 percent. Thus the oil feeding of said main circuit of said motor would be at the rate of 99.75 liter/min. total, and thus, the compensation is accomplished at 0.25 percent less than the designed capacity. Therefore, it is very effective. As an example, assuming each hydraulic motor is designed to feed oil at liter/min., but the hydraulic motors only feed at 95, 96, 97 and 98 liter/min. respectively owing to leakage of oil through gears and shafts thereof, the lack of oil, namely 5, 4, 3 and 2 liter/min. respectively must be fed into the main circuits to lift pistons thereof at the same height. For such purpose the How rate control variable restrictors with pressure controller 10, ll, 12 and 13 are provided. Therefore, the flow rate of the variable restrictors are initially adjusted to, namely 5, 4, 3 and 2 liter/min. respectively in this example, and these adjustments will never be changed throughout the lifting operation.

As the flow rate compensating circuits have to be capable of correcting the difference of the output of the motors in both lifting and lowering, each circuit is provided with a flow rate control variable restrictor l0, l1, 12 or 13, respectively, and a solenoid valve 15, which acts to change the direction, namely feeding in lifting or releasing (exhausting), at the time of lowering. Furthermore, the pressure at the outlet of the auxiliary pump 14 is arranged to be higher than the pressure in the main hydraulic circuits, thus enabling the liquid to be forced into the main circuit, even when only two of three cylinders bear all the load. 3. When an unbalance accidentally occurs in the cylinders 6, 7, 8 and 9 three cylinders are forced to share the whole load and the two diagonally placed cylinders have to share the concentrated load, with the one placed near the center of gravity of the load receiving maximum load.

The above-mentioned flow rate compensating circuit furnished at each cylinder will be utilized to rectify this inclined load.

For instance, when some heavy load is placed on a certain cylinder, the flow rate compensating afforded by the flow rate variable restrictor with pressure compensator of that cylinder, will decrease depending on the relative output pressures of the hydraulic pumps 1 and 14.

The delayed or lagging cylinder will be fed and recover its movement so that the load will be shared evenly among the cylinders.

4. When unbalance occurs at the lowermost terminal piston position of the cylinders 6, 7, 8 and 9, the preceding piston of the cylinder will stop first, but if other pistons of lagging cylinders are still making their lowering movement, the hydraulic motor of the preceding (leading) cylinder would continue its rotation. Thus, a state of vacuum in the circuit of said preceding cylinder would occurbetween the hydraulic motor and the cylinder. To prevent this vacuum state and maintain normal feeding, a liquid feeding circuit is connected to each main hydraulic circuit, between each cylinder and hydraulic motor independently, through the check valves 17, 18, 19 and 20, respectively. Moreover, unbalance at the upper terminal end of piston stroke will stop the hydraulic motor of the preceding cylinder unle the liquid in the circuit of said cylinder is released, therefore, an excess liquid release circuit is provided in the main hydraulic circuit. In other words, the common relief valve 25 is connected to each cylinder through each check valve 21, 22, 23 or 24 functioning independently to prevent any unbalance by releasing the liquid in the preceding cylinder. 5. Hunting phenomenon generally occurs in the cylinders through unbalance, thus resulting in an undesirable effect on synchronizing movement, at the start of the ascent or descent of the cylinders. This is caused by differences in the amount of the operating liquid in the hydraulic circuit of each cylinder or by unevenness of pressure effected by occluded air, for the prevention of which a test run has to be performed for a short period, before actual operation starts, in order to release the air and thus equalize the pressure. This should be done by changing the pressure in the relief valve 25 to the pressure equal to the set pressure of the relief valve 32 by the solenoid valve 26. In other words, a flushing circuit to correct unbalance at the start of cylinder movement is provided by connecting the hydraulic circuit through valves 25 to the relief valve 32, whose pressure is set lower than the set pressure of the relief valve 25.

Owing to the above-mentioned control circuit, this invention has solved any unbalance phenomenon which might occur in the hydraulic circuit, enabling heavy weight materials to be lifted or lowered under stable conditions.

The embodiment of the invention in which an exclusive property or privilege is claimed is defined as follows:

1. A hydraulically operated load-lifting apparatus comprising a source of hydraulic media under pressure, at least two hydraulic motors mechanically coupled together and connected to said source of media, hydraulicfiylinders, hydraulic main circuits each connecting one of sai motors to one of said cylinders, flow rate compensating circuits, flow rate control variable restrictors each interconnected in one of said flow rate compensating circuits and connected to one of said hydraulic main circuits whereby its compensating circuit feeds into or exhausts from its hydraulic main circuit depending on the pressure therein relative to the pressure in the compensating circuit, an adjusting circuit capable of correcting unbalances at the lower and upper terminal positions of said cylinders, a pair of relief valves in said adjusting circuit, common to all said main circuits with one relief valve set at the upper pressure of said cylinders and the other relief valve set at the lower pressure of said cylinders and check valves connecting said adjusting circuit to said main circuits.

2. A hydraulically operated load-lifting apparatus as claimed in claim 1 including liquid feeding circuits each provided in said adjusting circuit for one of said main circuits, a tank, and check valves each connecting one of said feeding circuits to said tank. 

1. A hydraulically-operated load-lifting apparatus comprising a source of hydraulic media under pressure, at least two hydraulic motors mechanically coupled together and connected to said source of media, hydraulic cylinders, hydraulic main circuits each connecting one of said motors to one of said cylinders, flow rate compensating circuits, flow rate control variable restrictors each interconnected in one of said flow rate compensating circuits and connected to one of said hydraulic main circuits whereby its compensating circuit feeds into or exhausts from its hydraulic main circuit depending on the pressure therein relative to the pressure in the compensating circuit, an adjusting circuit capable of correcting unbalances at the lower and upper terminal positions of said cylinders, a pair of relief valves in said adjusting circuit, common to all said main circuits with one relief valve set at the upper pressure of said cylinders and the other relief valve set at the lower pressure of said cylinders and check valves connecting said adjusting circuit to said main circuits.
 2. A hydraulically-operated load-lifting apparatus as claimed in claim 1 including liquid feeding circuits each provided in said adjusting circuit for one of said main circuits, a tank, and check valves each connecting one of said feeding circuits to said tank. 